As part of 1997's documenta city program, Michael Vorfeld and Hans Tammen created an immersive visual and sound installation in the Kassel planetarium, using the computer-controlled Zeiss 1015 planetarium projector, set against low-tech light sources such as incandescent lamps, fluorescent light, neon light, light boxes, torches, and slide projectors; and a surround sound performance created with a wide array of mechanical preparations (including brushes, small stones, electric fans, cigarette lighters, Ebows and chopsticks) from guitars, and a theremin.